Abstract
In the Australian grainbelt, early winter rainfall has declined during the last 30 years, and farmers sow their crops dry, increasing the risk of early season drought. This study aimed to examine whether differences in the root systems were associated with tolerance to early season drought. Three wheat cultivars with different root systems were grown in 1 m columns in a glasshouse. Immediately after sowing in dry soil, 440 mL water (equivalent to 25 mm rainfall) was supplied to each column, and no water was added to induce the early-season drought for the next 30 days. Shoot and root traits were measured at the end of the early season drought, anthesis and at maturity, respectively. The restricted water supply reduced Ψleaf, stomatal conductance, leaf photosynthetic rate, shoot and root biomass. Early season drought delayed phenology in all cultivars, but there was recovery of root and shoot biomass at anthesis in all three cultivars. Leaf area and shoot biomass at anthesis in Bahatans-87 (large root system) recovered better than Tincurrin (small root system). At maturity, early season drought reduced grain yield more in Tincurrin than Bahatans-87. The slow phenology of Bahatans-87 allowed greater recovery after the drought in leaf area and shoot biomass, which may explain the smaller reduction in grain yield after early season drought.
Highlights
Climate change is altering the pattern of the rainfall in the Australian grainbelt, affecting wheat production [1]
The slow phenology of Bahatans-87 allowed greater recovery after the drought in leaf area and shoot biomass, which may explain the smaller reduction in grain yield after early season drought
Wheat crops sown into dry soil will germinate at the first rainfall, which could leave crops vulnerable to 20–32 days of drought after emergence
Summary
Climate change is altering the pattern of the rainfall in the Australian grainbelt, affecting wheat production [1]. In the Australian grainbelt, drought spells often occur early in the season [2], mid-season (from stem elongation to two weeks before flowering) [3] and from flowering (terminal drought) [4]. Sowing is common practice in the Australian grain belt, allowing wheat crops to escape the severe effects of terminal drought on grain yield [5]. Early winter rainfall in the Mediterranean-type climate of Australia has declined and in response, 82% of wheat growers are sowing all their crops into dry land [2]. Wheat crops sown into dry soil will germinate at the first rainfall, which could leave crops vulnerable to 20–32 days of drought after emergence (i.e., early season drought, ESD). ESD reduces the rate of leaf net photosynthesis, tiller number, leaf area, aboveground biomass and grain yield [8,9,10] as well as below ground traits, such as, total root length and root surface area, increases the root: shoot ratio [11]
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